More recycling not the solution to reducing aluminum’s carbon footprint

Aluminum cycle accounts for just over 1% of global greenhouse emissions.

It’s one thing to finally muster the resolve to take action to curb the effects of climate change. It’s another thing to actually get it done. One commonly discussed goal (perhaps drifting out of reach) is holding warming under 2°C, beyond which researchers say the damage adds up much more quickly. To do so, overall greenhouse gas emissions need to drop to less than half of what they were in 2000 by the year 2050. But can every source of emissions achieve that reduction?

A new analysis published in Nature Climate Change zeroes in on one significant source of emissions—the aluminum industry. In the same way that we can think about Earth and ecosystem processes like the carbon cycle or the nitrogen cycle, the paper lays out an economic aluminum cycle (with a fantastic figure). Aluminum is mined and processed, turned into raw products used in the manufacturing of goods, and ends up somewhere at the end of its useful life. The researchers modeled the cycle and the results showed that reducing emissions throughout the cycle will be tough.

The first product that comes to mind when you consider aluminum might be beverage cans, but that accounts for a pretty small piece of the pie. And while many aluminum products are effectively recycled, a fair amount of the metal still ends up in landfills. Indeed, Aluminum has become a poster child for recycling in general, since the smelting of aluminum ore is such a voracious consumer of energy.

Smelting is where the majority of the emissions are generated. Recovering pure aluminum from ore requires huge amounts of electricity, often supplied by coal-burning power plants. (Though the aluminum industry is huge in Iceland, despite its lack of ore, due to its plentiful geothermal and hydroelectric capacity.) And it all adds up—this aluminum cycle accounts for a little over one percent of global greenhouse gas emissions.

Because that process is so expensive, the industry has a strong incentive to recycle. Over half of the raw aluminum that enters the manufacturing sector comes from recycled material. Still, two-thirds of that is pre-consumer scrap—waste from the manufacturing process—rather than post-consumer scrap like beverage cans and automobiles. “Only post-consumer scrap recycling has the potential to significantly lower total energy use and emissions,” the researchers from the Norwegian University of Science and Technology write.

To project how changes to this industry could affect emissions in the future, the researchers constructed a model of the aluminum cycle, using it for nine different scenarios covering the spread of potential future changes to global aluminum demand. For each scenario, they evaluated the effectiveness of emissions-mitigation strategies such as capturing more post-consumer aluminum for recycling, making the smelting process more efficient, and using cleaner sources of energy to satisfy the remaining demand for electricity.

The 50 percent emissions reduction relative to 2000 goal was only achieved in one of the nine scenarios—the one with the lowest future demand. Technological advances simply cannot sufficiently offset the effect of increasing demand to hit that target.

In the model, long-term trends in emissions were controlled by recycling efficiency and aluminum demand, so improvements to the smelting process only had an impact in the short-term. The researchers point out that this means those improvements would have to be realized in the near future for the benefits to really outweigh the development costs. Their value depends on rapid implementation—a fact that seems likely to apply to other industries, as well.

The relationship between emissions and economic activity

A letter in the same issue of Nature Climate Change demonstrates a separate point relevant to understanding future emissions patterns. Some emissions projections make a simplifying assumption: emissions increase as GDP rises, and decrease at the same rate when GDP falls. The author, Richard York of the University of Oregon, writes, “…CO2 emissions depend not only on the size of the economy, but also on the pattern of growth and decline that led to that size.”

For an example, one needs look no further than the recent economic recession. “This may help explain in part the observation that the reduction in global CO­2 emissions in 2009 following the global financial crisis was modest compared with the increase in emissions in 2010.”

York surmises that this is at least partly due to the fact that many things purchased during times of economic growth—like cars, for example—hang around even if new purchases slow. Regardless, as GDP fluctuates in the future, emissions will keep ratcheting up.

These details—how emissions track economic output and how aluminum demand will affect efforts to reduce emissions—matter as we try to chart a future course that minimizes additional warming. Knowing the lay of the land is necessary to efficiently get from point A to point B. Doubly so when the clock is ticking.